In typical manufacturing processes, a large number of semiconductor devices are formed on a singe wafer. After the semiconductor devices are formed, the wafer is sliced and diced so that each individual semiconductor device is separated from the others formed on the wafer. The individual semiconductor devices are then packaged. Packaging provides physical protection and also dissipates heat from the semiconductor. The packaging, for example, in flip chip technology, also provides leads between individual chips and an exterior of the package. The leads provide electrical connection between the chip and a printed circuit board or other device.
In flip chip technology, for example, a series of C4 bumps are formed in an array on a surface of the flip chip. In the packaging, the C4 bumps are attached to a substrate. One method of such packaging includes underfill. In fact, underfill is required for almost all C4 products to, for example, prevent C4 corrosion and C4 fatigue fails due to thermal mismatch.
The standard industry process to apply underfill is through a capillary flow underfill process. In this process, underfill is dispensed along one or multiple edges of the chip and then flows under the chip by capillary action. However, it is known that the flow of the underfill is irregular and unpredictable and can lead to voids around C4 bumps. These voids can allow for C4 corrosion and dendritic growth, as well as thermal fatigue of C4s due to CTE mismatch between the chip and the substrate. These problems can ultimately lead to device failure and yield loss.
For example, as shown illustratively in FIG. 1A, during the capillary action the underfill has an irregular flow front, which becomes even more pronounced in finer pitched C4 products. As different portions of the flow front converge, voids or air pockets can develop around the C4 bumps, as shown in FIG. 1B. Analysis under acoustic microscopy has shown that flow fronts of the underfill can converge, resulting in entrapped air (caused by the non-uniform underfill flow). Large entrapments of air or voids are considered yield loss. The entrapment of air due to non-uniform underfill flow underneath the chip is of especial concern for fine-pitch solutions, which are required for newer technology chips.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.